The following diagram illustrate temperature measurement,
where T is the total amount of energy distributed among N atoms. When thermal equilibrium is reached with another body of n atoms, we have a measure,
K=T+ToN+n
obviously,
K=T+ToN+n≠TN
When T is large or N is large then
T+ToN+n≈TN
but when T is small or N is small, the measurement fails.